A liquid crystal display is a passive light emitting device and composed of a liquid crystal display panel and a backlight source, wherein the display luminance of the liquid crystal display panel is determined by the luminance of the backlight source. Most existing liquid crystal displays have a fixed luminance during display, and as a result, when the light intensity of an ambient light is high, the display effect is poor or even unsuitable to be viewed.
In order to improve the adaptivity of a liquid crystal display to the ambient light, the existing liquid crystal displays are provided peripherally with an optical sensor for detecting changes in the light intensity of the ambient light so as to control the brightness of the backlight source depending on the detected changes in the light intensity of the ambient light. For example, when the light intensity of the ambient light is higher than a threshold, luminance of the backlight source can be turned up, and when the light intensity of the ambient light is lower than a threshold, luminance of the backlight source can be turned down. However, such a liquid crystal display may have a problem. When the liquid crystal display panel has a very large screen, it is possible that the screen is only locally irradiated by intense light. In this case, it is impossible to adjust only the luminance of the backlight source corresponding to this region. Therefore, the image quality of the region irradiated by intense light in the screen will be severely affected, or even cannot be normally viewed.